CN104487799A - Interferometric distance measuring arrangement and corresponding method - Google Patents

Interferometric distance measuring arrangement and corresponding method Download PDF

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Publication number
CN104487799A
CN104487799A CN201380039375.2A CN201380039375A CN104487799A CN 104487799 A CN104487799 A CN 104487799A CN 201380039375 A CN201380039375 A CN 201380039375A CN 104487799 A CN104487799 A CN 104487799A
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distance
passage
measuring device
optical unit
wavelength
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CN104487799B (en
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托马斯·延森
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Hexagon Technology Center GmbH
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Hexagon Technology Center GmbH
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/0209—Low-coherence interferometers
    • G01B9/02091—Tomographic interferometers, e.g. based on optical coherence
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/14—Measuring arrangements characterised by the use of optical techniques for measuring distance or clearance between spaced objects or spaced apertures
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02001—Interferometers characterised by controlling or generating intrinsic radiation properties
    • G01B9/02002—Interferometers characterised by controlling or generating intrinsic radiation properties using two or more frequencies
    • G01B9/02004—Interferometers characterised by controlling or generating intrinsic radiation properties using two or more frequencies using frequency scans
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02015—Interferometers characterised by the beam path configuration
    • G01B9/02027—Two or more interferometric channels or interferometers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02041—Interferometers characterised by particular imaging or detection techniques
    • G01B9/02044—Imaging in the frequency domain, e.g. by using a spectrometer
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02049—Interferometers characterised by particular mechanical design details
    • G01B9/0205—Interferometers characterised by particular mechanical design details of probe head
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02055—Reduction or prevention of errors; Testing; Calibration
    • G01B9/02056—Passive reduction of errors
    • G01B9/02057—Passive reduction of errors by using common path configuration, i.e. reference and object path almost entirely overlapping

Abstract

The invention relates to an interferometric distance measuring arrangement for measuring surfaces, using at least one laser which can be tuned for generating measurement radiation modulated by a wave length ramp, an optical beam path with an optical transmitting system for emitting the measurement radiation to the surface and an optical capturing system for capturing the measurement radiation back-scattered by the surface, comprising a measuring arm and a reference arm and a radiation detector and an evaluation unit for determining the distance from a reference point of the distance measuring device to the surface. Channels are defined by at least one beamsplitter (13, 29) n >= 2 for the parallel emission of measurement radiation, respectively, one different sub area of the wave length ramp is allocated to said channels at a predetermined emission time point.

Description

Interference distance measurement mechanism and corresponding method
The present invention relates to the interference distance measurement mechanism for measured surface as described in the preamble according to claim 1, and relate to corresponding method as described in the preamble according to claim 11.
In many applications, need to measure body surface with pin-point accuracy, and measure object itself thus.This is applied to process industry, and specifically, its high importance is bonded to the surface measured and check workpiece.For this application, there is many measurement mechanisms, it designed to be used specific task, and is designated as coordinate measuring set or machine.These measurement mechanisms are by setting up Mechanical Contact and scanning of a surface measures this surface.Its example comprises Gantry measuring machines device, for example, as described in DE 4325337 or DE 4325347.Different systems can along the joint arm of surface movement based on survey sensor that is used, that be arranged on many qis arm end.General joint arm is such as described in US 5402582 or EP 1474650.Other method uses optical measurement radiation, so that can scanning of a surface non-contiguously.
According to a kind of known method of prior art at this based on interference technique, for example, as optical coherence tomography fault imaging (OCT), such as, be describe in the european patent application of 11171582.7 at WO 2009/036861 or application number.Distance measurement method disclosed herein, for the object of measured surface, uses laser of frequency modulation bundle, to provide the measuring radiation be transmitted on surface.Again received from the measuring radiation of this backscatter,surface and for measuring the distance (that is, along so-called z direction) from reference point to this surface with interference mode, wherein, employed gage beam and reference arm.
In most of illustrative embodiments, this surface is scanned by means of the single-measurement passage measuring this distance more on the surface, and wherein, this surface is by realizing mobile on the path of whole detection termination measurement point on a surface.But, for the diversity of application, need simultaneously or in extremely rapid succession scan relatively a large amount of points by distance measuring method, and this forces and mobilely in order with optical system on each point that will measure detects termination.
Be to utilize one dimension or Scan mirror according to a kind of method that prior art is known, so that can traverse measurement beam from the teeth outwards, and do not need to force mobile detection termination or whole measurement mechanism.Realizing such as at " the MEMS-based endoscopicOCT " of the people such as J.Sun with the correspondence for the micromechanical component of interferometric measuring means of medical domain, Int.J.of Opt., is described in 2011.But these shortcomings based on the solution of mirror are objects that order scanning space is wide still, which reduce the speed that can realize.Only by means of the sweep speed increased or by means of using the measurement processing of multiple passage and parallelization orthogonally to improve.
Therefore, the course of the beam that WO 2009/036861 describes wherein measuring radiation is divided into two passages, the detection termination of transmitting and receiving direction orientation relative to one another, and achieves the detection termination of multiple spatial parallelism passage.In these methods, this treatment channel can walk abreast or sequentially Interim use, wherein, any two or more separating and treating apparatus, or alternatively, have the single treating apparatus of split tunnel such as by means of different polarization direction, situation about using at the same time is fine.So a kind of embodiment of detection termination such as allows to measure edge or step.But, to be correlated with the result be separated as polarization, this complex structure and the number of channels that can realize is limited.
About fundamental measurement principle, for optical coherence tomography, known extremely fast tuning source, for example, as " Megahertz OCT for ultrawide-field retinal imaging with a 1050nmFourier domain mode-locked laser " people such as T.Klein, Opt.Express 19, described in 3044-3062 (2011), also known have high-speed line CCD's, the extremely fast method of spectral resolution is shown at Fourier domain, for example, as " High-speed complex conjugate resolved retinal spectral domain opticalcoherence tomography using sinusoidal phase modulation " people such as Y.K.Tao, Opt.Lett.32, described in 2918 (2007).
But two kinds of methods illustrate and lack available coherent length, such as, as needed for industry measurement field, in general coordinate measuring machine or device.
For have broad band source, optical coherence tomography in time domain (time domain OCT), due to short-phase dry length, thus, this additional scanning that will need in the z-direction, namely, along the surface normal wanting measured surface, it needs again the complicacy of driving and the increase added, reference, " the Three-dimensional sensing ofrough surfaces by coherence radar " of the people such as T.Dresel, Appl.Opt.31,919 (1992).
Have spectral resolution, optical coherence tomographic imaging method in frequency domain (frequency domain OCT) with regard to they for parallel scan ability with regard to, can also be developed by using the area sensor that replaces line sensor.But the low typical coherent length of low frame rate or reading speed and same about a few micron dimension is disadvantageous at this.
In this case, the method for frequency modulation OCT can also be enhanced to two dimension or 3-D scanning scope by using line sensor or area sensor.Because due to the reason needing scanning to have the interferogram of a hundreds of data point, and perfect measurement also forces needs to carry out corresponding record hundreds of data fields by means of line sensor or area sensor in this case, so compared with common FD-OCT method, this method is (<100Hz) slowly, such as, with reference to " the Line-field optical coherence tomography using frequency-sweepingsource " of the people such as S.W.Lee, IEEE J.Selec.Top.Quant.Electr.14,50 (2008).
At this, still, for detecting the design of termination in Free Space Optics, these data are generated by line sensor or area sensor a main total shortcoming.This means, its no longer can utilize by the connection of single-mode fiber spatially divide detection termination and signal generate and signal transacting.Except caused detection termination increase complicacy and increase except quality, specifically, the end of probe hair heat caused because of current drain has adverse effect.In coordinate measuring technology field, for the assembly of movement from the teeth outwards, as far as possible passively to be formed, therefore, there will not be the heat affecting of the supporting body malformation made for movement.And the moving assembly (and, specifically, detection termination) of wanting of low weight causes the dynamic range improved, and causes the less acceleration related variation of bearing structure.
An object is, provides a kind of for measured surface or for the improvement distance-measuring device that detects surface topography or corresponding measurement mechanism and corresponding method.
Another object is, provides so a kind of and improves distance-measuring device, and a kind of so method, that is, it allows in conjunction with the structure of low-complexity and the bearing structure of low thermal force to measure multiple or multiple point, and does not need mobile detection termination.
These objects realize by means of the purport of claim 1 and 11, or this solution is developed by the purport of appended claims.
The present invention uses the interferometric principle utilizing lasing light emitter, and this lasing light emitter for this wavelength-modulated, that is, utilizes variable wavelength to launch, and wherein, this measurement is pressed frequency domain and performed.In this case, by the laser emission that generates as the laser instrument (such as, laser diode) of lasing light emitter according to the wavelength slope of process and the radio optics frequency that changes thus modulate.Such as, Sine Modulated is added on centre wavelength or optical frequency.Then, measured interferogram such as this modulating frequency, semiperiod that wherein optical frequency rises monotonously or declines is estimated, it is also called as wavelength slope below.Because tuned laser is as the source of unusual narrow-band, thus, all interference effects are arranged in same coherent ranges.
In this case, this wavelength slope can be embodied as traditional slope, that is, the substantial linear with the wavelength that will pass through rises or descending order.But alternatively, all right Stochastic Modulation of this group different wave length, that is, modulate by the mode of the orderly order of departs from linear, as long as this group wavelength is detected and modulates once during the skew of slope.Therefore, term wavelength slope covers a different set of like this wavelength in more broad sense, that is, it can cause increasing or decreasing continuity veritably, and need not by this continuity through and modulation.But a preferred implementation is designed with the sequence of the linear ramp alternately rising and decline.
Be suitable for its method and assembly WO 2009/036861 or there is application number 11171582.7 european patent application in be described.The present invention is based at least two the optical delivery passages realizing can also being used to receive, wherein, the interim transmitted in parallel of measuring radiation occurs.According to the present invention, for the x time of specifying, each passage is assigned with the subrange of the wavelength slope that will pass through, that is, wavelength and frequency band, and it is assigned the radiation of launching by this moment of the wavelength will modulated for it.
Each passage can be assigned the stator scope of this wavelength slope, and it is the process for the measuring radiation via this channel emission only, that is, the measuring radiation via other channel emission does not utilize this part of this wavelength slope to modulate.Compared with this wavelength slope, perform modulation with less skew, that is, this wavelength slope is divided into slope, discrete local, and whole modulation is divided into local modulation.In this case, this wavelength slope can separate it all along all passages, that is, the wavelength shift utilizing every passage uneven equably or unevenly.But in principle, for other object, a part for this wavelength slope can also continue to keep not using or using, such as, for internal calibration or reference measurement.The components side of the method realizes such as to be separated by look by means of beam splitter realizing, specifically, also by the beam splitter of stepped sequence.As generating to the result that their fixed frequency spectrum divides after radiation, the separability of this passage rises thus statically.
As a result, the multiplexing wavelength slope using the larger width (100nm to 200nm) of useful source thus of the look caused, it is divided into multiple subrange.Although this available coherent length not affecting the dynamic linewidth according to modulated laser and arrange, it reduces spatial resolution in parallel degree.Because optical coherence tomography is in the pin-point accuracy (3 σ ~ 20-30nm) of spatial frequency domain, the reduction thus for the accuracy of measurement of technical face can accept usually, and without any problem.
According to the present invention, therefore, by means of at least one look beam splitter, be defined for the passage of parallel launch measuring radiation, it selects x time to be assigned the different subranges of described wavelength slope for one in each case.Each passage has the different spectral distribution that frequency spectrum presents by this selection x time in its output (that is, along transmit direction), thus, have different color characteristics.For the situation that the look of the discrete wavelength scope with static allocation is separated, by the x time under consideration, so, the passage launched is only that correspondence passes through the wavelength coverage of its wavelength slope and a described passage of subrange in this moment.Such as, thus frequency spectrum is in said device separated and carries out discretely, in the scope of 2 μm to 10 μm, to make to limit discrete range, wherein, can estimate constant phase gradient.
In addition, this look multiplexing can be combined with frequency division multiplexing, and wherein, the possible measurement range predetermined according to coherent length (that is, the TMD that can realize) is separated, to make zero position for each channel shift as a result on distance side.Each passage utilizes its corresponding fathoming and is assigned the subrange of described measurement range thus, and the corresponding displacement of the known zero position for a passage, can take in it is measured or estimates thus.Thus, although there is different zero positions when smooth surface, this passage measures the distance identical with net result, for this object, by means of delay section, before signal transacting, generate different staggered distances, this distance is known, and therefore takes in when estimating.In other words, for the reference point of this measurement from passage to channel shift, but can computationally mate.This staggered greatest limit is also limited by coherent length by maximum measurement range thus at this.
Postpone by means of the difference for this passage, the measurement range limited by coherent length is divided into single part, and coherent length is segmented thus.When the commercial measurement for the opaque surface of measuring radiation (specifically, for metal surface), fourier spectrum or tomographic X-ray photo only show single largest value under normal circumstances.Thus under frequency domain, the major part in space is not used to measure.Due to the appointment coherent length in this source, thus parallelization can realize by means of separating whole usable measurement range.In this case, can keep realizing accuracy, in principle, as the result that this separates, energy distributes between different passage, although this can compensate by using amplifier.
Zero point for different passage has embodiment compact in structure by means of the displacement (it is called as frequency division multiplexing) postponing to divide section, wherein, carryover effects is realized by the different paths in medium (for example, as glass).
In addition, in order to avoid crosstalk, can use and relevant postpone section, its relative length spacing between continuous passage is greater than coherent length in each case.
Thus, according to the present invention, interference distance measurement mechanism can be realized according to the optical coherence tomography principle under frequency domain, wherein, for the situation of parallelization measurement processing, it becomes and can realize detecting being separated and connection of termination and signal transacting via single single-mode fiber.The detection termination of movement from the teeth outwards to can generate by electronic passive mode thus, and can not thermal force be produced.Specifically, use look multiplexing, also with frequency division multiplexing combinedly, make its level can measured by a single point, utilize the line style of passage or matrix type device to keep the measurement speed measured for parallelization.
Below, based on schematically illustrative illustrative embodiments in accompanying drawing, completely by the mode of embodiment, distance-measuring device according to the present invention is described in more detail or is illustrated, specifically, wherein:
Fig. 1 shows the schematic illustration figure for the interferometric measuring means in the measurement mechanism of measured surface according to prior art;
Fig. 2 shows the illustration figure of the structural architecture of the detection termination for corresponding measurement mechanism;
Fig. 3 show for corresponding measurement mechanism transmission and receive the schematic illustration figure of optical unit;
Fig. 4 shows the illustration figure of the structural architecture of the detection termination for distance-measuring device according to the present invention;
Fig. 5 shows the schematic illustration figure of the Part I for basis with the course of the beam of the first illustrative embodiments of the distance-measuring device of the present invention of the spectral range of static allocation;
Fig. 6 shows the schematic illustration figure of the Part II of the course of the beam of the first or second illustrative embodiments for distance-measuring device according to the present invention;
Fig. 7 shows the schematic illustration figure for the transmission of distance-measuring device according to the present invention and the aperture arrangement of reception optical unit;
Fig. 8 show for the wavelength slope distributing to passage different subranges, the schematic illustration of the relation Butut of institute's detected intensity and wavelength;
Fig. 9 a-c shows the schematic illustration figure with the 3rd, the 4th and the 5th illustrative embodiments of static allocation according to distance-measuring device of the present invention;
Figure 10 show for distance-measuring device according to the present invention, the schematic illustration figure of the Part II of the course of the beam of the 6th illustrative embodiments with additional delay section;
Figure 11 shows the schematic illustration figure of the Part I of the course of the beam of the 6th illustrative embodiments for distance-measuring device according to the present invention;
Figure 12 shows the schematic illustration figure for the transmission of the 6th illustrative embodiments of distance-measuring device according to the present invention and an illustrative embodiments of reception optical unit;
Figure 13 shows the schematic illustration figure of the E field distribution under frequency domain of the 6th illustrative embodiments for distance-measuring device according to the present invention; And
Figure 14 show for distance-measuring device according to the present invention the 6th illustrative embodiments, according to the schematic illustration figure of the distribution of institute's detected intensity of multiple interferograms under frequency domain.
Fig. 1 shows the schematic illustration figure for the interferometric measuring means in the measurement mechanism of measured surface according to prior art, for example, as WO 2009/036861A1 or there is application number 11171582.7 european patent application in describe.This device uses wavelength-modulated laser instrument (specifically, only single laser instrument, such as, laser diode) as the lasing light emitter 1 for generating at least one laser beam and for receiving the radiation detector 5 from surface 4 backscattered measuring radiation MS.In this case, this modulated laser source is preferably designed to, laser instrument is as used herein made to have the coherent length being greater than 1mm, specifically, in the scope of 1 millimeter to 20 centimetres, such as, when 60nm or more coherent length, be less than the dynamic linewidth degree of 0.02nm, centre wavelength between 1.3 μm and 1.7 μm, and the tunable wavelength scope being greater than 40nm.Thus, this coherent length also allows to measure in the degree of depth of several centimetres or distance range.
The laser emission generated by lasing light emitter 1 is coupled in the interferometer structure for measuring via optical circulator 2, described interferometer structure utilizes common path geometry specifically to implement, such as, in other words, there is the local public interference instrument course of the beam for gage beam and reference arm.In this case, this reference arm limits according to the reflection at the light exit surface place of gradient-index lens, makes the distance limiting constant (particularly, known), wherein, avoids further back reflection.Therefore, this reference surface is arranged in sending/receiving optical unit 3, and this sending/receiving optical unit is at the assembly for being integrated with transmission and reception optical unit in the beam-shaping optical unit of Emission Lasers bundle.By contrast, this gage beam limits according to the reflection at surface 4 place that will measure.The back reflection light of gage beam and reference arm is finally delivered on radiation detector 5 via optical circulator 2 again, and it is preferably embodied as the InGaAs detecting device with the bandwidth being greater than 100MHz.Finally, the distance measured can be determined in estimation unit (not illustrating at this).
In addition, can also use the calibration interferometer (not illustrating at this) with fluorescence detector, it is considered or compensates the non-linear of tuning behavior, and wherein, described calibration interferometer can be implemented as etalon or Mach-Zehnder structure.
This distance-measuring device such as can be integrated in the detection termination for the coordinate measuring set of scanning survey, for example, as known from WO 2009/036861A1.Fig. 2 shows the structural architecture of this detection termination for corresponding measurement mechanism.In this case, this coordinate measuring set has the guiding device for guiding detection termination on the surface that will measure by the scan mode limited, and this detection termination has at least one the transmitting and receiving course of the beam of the measuring radiation MS for launching interference distance measurement mechanism.
This detection termination is by scan mode, guide in the mode by limiting as arm part components 9 and the joint 8 of guiding device on the surface that will measure, and wherein, this joint 8 can also rotate relative to arm parts 9.Rely on the rotation relative to arm parts 9 and joint subsequently 8, the surface topography of horn shape or greatly change easily can be followed in detection termination.But, principle can will further to rotate or translation freedoms is integrated in this guiding device, to make it possible to the guiding improving detection termination further.
This detection termination has at least one face side transmitting and receiving course of the beam of measurement beam MS.In this illustrative embodiments, this beam is conducted through the tubule as exploring block 7, and it comprises sending/receiving optical unit.In detection termination, adjacent with described pipe thick base portion 6, in fact radiation detector itself can be set, otherwise the optical waveguide just arranged for relaying to the radiation detector being integrated in other place, wherein, interchangeability is guaranteed with the signal between joint 8 with the optics be coupled and/or the electric interface transmitted for detecting the base portion 6 of termination.
Fig. 3 schematically shows and is integrated in the pipe of detection termination by sending/receiving optical unit.In such configuration, optical fiber 7a is for guiding the measuring radiation of measuring radiation and the guiding internal reflection that will launch and externally being reflected and again received measuring radiation MS.In this case, this is emitted through gradient-index lens 7b and occurs, and it is arranged in tubular part, and its by radiative emission to wanting, on measured surface 4, then the measuring radiation MS reflected therefrom to be coupled in optical fiber 7a again.But the solution of prior art mainly only designs for single measurement, wherein, continuous detecting can also be carried out by the detection termination effects on surface guided by scan mode.
But, allow to improve parallelization according to method according to the present invention and realize multiple or multiple separation and can estimate Measurement channel, possibility is become in conjunction with simple structure structure to make the structural architecture of the detection termination 10 as shown in Figure 4 with multiple passage, wherein, by means of at least one beam splitter, define for transmitted in parallel and particularly also for n >=2 passage of parallel reception measuring radiation, it in all cases, the different subrange of described wavelength slope is assigned for given x time, to make to realize that there is special separation estimation and the independent reception of range observation for each passage.
Comprise, according to the detection termination 10 of distance-measuring device of the present invention, there is base portion 10a now, wherein, lasing light emitter can be set and estimate electronic installation.But alternatively, these assemblies can also be the parts of the different assembly of this measurement mechanism, wherein, then arrange via one or more interface the joint 8 detecting termination 10 to be connected with the optics between base portion 10a and/or electronics.Preferably, the base portion 10a of detection termination is connected to optical unit parts 10c via connecting pipe 10b, and wherein, this connecting pipe 10b has photoconduction.But, alternatively, the device departing from it can also be used to realize according to distance-measuring device of the present invention.In this, such as, can also all component of detection termination 10 be concentrated in single compact unit, to make omission connecting pipe 10b.
Thus detection termination 10 comprises according to the whole of the interference distance measurement mechanism for measured surface of the present invention or most assembly, wherein, configures described device specifically according to optical coherence tomography principle.For this reason, the lasing light emitter dependence for tunable wave length is modulated, to generate measuring radiation MS by other continuity a certain (needing not to be linear) selection wavelength through the modulation of linear wavelength slope or from a different set of wavelength.Optical beams path is formed in detection termination 10, wherein, for the transmission optical unit that is transmitted into by measuring radiation MS on surface be used for receiving and be formed on optical unit parts 10c from the reception optical unit of the measuring radiation MS of backscatter,surface.In this case, transmitting optics unit and reception optical unit preferably use same components, to make two optical units be embodied as the transmitting and receiving optical unit of combination by Integrated design, it is coupled to radiation detector via single single-mode fiber particularly.Gage beam and reference arm limit or are formed in by mode same as the prior art in course of the beam, and wherein, this interferometer is specifically provided with the public course of the beam in local of gage beam and reference arm, as common path interferometer.Detect outside termination for determining that radiation detector from the reference point of distance-measuring device to this surface and estimation unit can be arranged on the base portion 10a detecting termination 10 or be arranged in addition, wherein, in the later case, detection termination eliminates electronic package, and can keep completely passive thus.
In base portion 10a, laser emission can by least one beam splitter separately, to make at least two passages being defined for transmitted in parallel measuring radiation MS, it is assigned the different subrange of described wavelength slope in each case for given x time according to the present invention.This means, and for given time, each passage is assigned the different wavelength coverage for this passage, to modulate this measuring radiation.In this case, all passages side by side or are continuously launched during the process through wavelength slope.For this reason, wavelength slope can be divided into the identical many frequency bands of width, and its quantity corresponds to port number, and wherein, each passage is assigned with a wavelength band.But, alternatively, wavelength slope or the scope of the spectrum modulation degree of depth can also continue to keep not using, or to use outside passage for different object, such as, non-linear for what determine to modulate.Similarly, wavelength slope can statically or dynamically divide according to the different subrange of the width being assigned to different passage or frequency band unevenly.In this way, such as, the passage with different measuring characteristic can be realized, such as, if when measuring boring, for realizing with the passage of high-acruracy survey inside surface and the low accuracy channel parallel for the longitudinal axis of location drilling.Similarly, these passages can be assigned the frequency band of different in width temporarily, make it possible to achieve measurement range or the accuracy of measurement of Iterim Change.
Fig. 5 shows the Part I of the course of the beam of the first illustrative embodiments for distance-measuring device according to the present invention, and described Part I is formed in the base portion of detection termination.In this first illustrative embodiments, wavelength slope is divided into the identical many wavelength bands of width, and its quantity corresponds to port number, and wherein, the subrange of this wavelength slope is separated by look and generates.For this reason, the laser emission generated by the laser of lasing light emitter is via optical fiber and be coupled in the array waveguide grating as beam splitter 13 for the sleeve pipe 12 of this single optical fiber, and it is arranged in the shell 11 of base portion.This array waveguide grating can by being subdivided into different branch by tuning range or wavelength slope or subrange quality in next life is multiplexing.For the tuning range between 1500nm and 1600nm, the component from the field of telecommunications for c and l frequency band can be used.In this, array waveguide grating uses in this scope, passage to be divided into the so-called ITU passage of different separation.In this case, the width of passage depends on used ITU standard, and described width range changes from 50,100 or 200GHz to a few nanometer.This beam splitter makes it that the look of laser emission or frequency spectrum can be realized to be separated into different passages, and specifically, multiplexor, wherein, the array waveguide grating as beam splitter 13 works as compact spectrometer.At the efferent place of beam splitter 13, the measuring radiation being divided into multiple passage is coupled in single optical fiber 15 via many ferrules 14, and wherein each is assigned with described frequency or wavelength range delta lambda 1-Δ λ none of.Optical fiber 15 is directed in the optical unit parts 10c of detection termination via connecting pipe 10b, exemplified with described optical unit parts in Fig. 6 as fibre bundle 16.
Described Fig. 6 is exemplified with the Part II of the course of the beam of the illustrative embodiments for distance-measuring device according to the present invention, and wherein, the division in base portion is followed successively and is coupled in optical fiber 15.Via connecting pipe 10b guide optical fiber 15 via single ferrule 18 optical unit parts 10c shell 17 be internally coupled in the route of gradient-index lens 19, thus, measuring radiation is with wavelength range delta lambda 1-Δ λ 10launch, they are different for each (at this, according to first illustrative embodiments) in ten passages of this illustrative embodiments.The position of the local oscillator of this reference arm can by such as transitting to gradient-index lens 19 from sleeve pipe 18 otherwise limiting in the suitable reflective isolating coating transitting to air from gradient-index lens.It is maximum overlapping that the course of the beam of reference arm and gage beam is shown for common path geometry thus.By means of the assembly for transport process, received equally from the measuring radiation of surperficial back reflection, this detection of result termination realizes the integrated sending/receiving optical unit with ten lenticular row, wherein each distributes coloured separation and one of Measurement channel estimated separably, to make to realize multiple transmission and receiving cable.Because available coherent length does not weaken because look multiplexing, so there is the great dirigibility of the configuration that relevant beam guides, wherein, each passage can such as design for collimation or beams intersect section independently.
But, as the alternative case of the line like manner of Fig. 6 shown device, can also use for distance-measuring device according to the present invention transmission and receive the rectangular aperture arrangement 19' of optical unit, as schematically illustrated in Fig. 7.Utilize this two-dimensional microlens or aperture arrangement, specifically, regional expansion structure can fast and measure by parallel mode.
When Fig. 8 shows multiplexing in a frequency domain, for wavelength slope, the different subrange Δ λ that distributes to passage 1-Δ λ 10, the schematic illustration figure of the time correlation distribution plan of the intensity I (λ (t)) detected and wavelength X (t).This intensity distribution is divided into different less interferograms thus.During signal transacting, the intensity distribution recorded is divided in multiple passage, and discretize thus, wherein, each passage is separated process subsequently.The geometry barycenter that this object is by means of Fourier transform and frequency domain determines the frequency of path interferometric figure.Determined frequency target range in proportion to, that is, for the distance on the surface that will measure.
Fig. 9 a-c schematically illustrates the 3rd, the 4th and the 5th illustrative embodiments according to distance-measuring device of the present invention.Except the detection termination utilizing multiple passage as shown in Figure 6, the passage of smaller amounts can also be realized according to the present invention, such as, suppose this satisfies and measure application accordingly.In this case, this look beam splitting can also send optical unit, be directly arranged in launch upstream side assembly in realize.By means of the look beam splitter with the layer coordinated towards corresponding separation, along course of the beam, corresponding passage can separately also be guided along different directions thus.This passage is thus by means of utilizing the beam of the layer coordinated along with corresponding separation separately to be separated.
In this, Fig. 9 a-c shows three different illustrative embodiments, and wherein, optical fiber is always connected to gradient-index lens 19' via sleeve pipe 18', and laser emission is modulated in the wavelength coverage of 1500nm-1600nm.Subsequently, in Fig. 9 a-b, the first passage with the wavelength band 1500nm-1550nm of the subrange as wavelength slope is coupled out from course of the beam by beam splitter 20, and wherein, the residue subrange with wavelength band 1550nm-1600nm is launched by as second channel.
For this reason, in figure 9b, transmit direction is deflected by mirror surface or interphase 20', as a result, this device can be used to such as scan the cylinder openings in boring or engine, wherein, owing to launching along two reverse directions, thus, detection termination only rotates the half just whole circumference of satisfied scanning.
Fig. 9 c shows like configurations, but, wherein, amount to three passages (there is wavelength band 1500nm – 1533nm, 1533nm – 1566nm and 1566nm – 1600nm) and " limit by means of two beam splitter surfaces 20.
In whole three illustrative embodiments in Fig. 9 a-c, during the aligning carrying out measuring radiation for each passage, the end be used as in the end of the local oscillator of reference arm can be limited by the exit surface LO of measuring radiation, and result causes make use of for the to a great extent identical course of the beam of gage beam with the common path geometry of reference arm.But, according to the present invention, other beam can also be used to guide (specifically, beam deflection) and different beam-shapings, such as, by measuring radiation being focused on the surface.
Look divide principle can in addition and frequency-division multiplexing method combined, as having described in the european patent application of submission number 1739811 and application number EP12177582.9.In this respect, Figure 10 and Figure 11 shows the schematic illustration figure of the 6th illustrative embodiments for distance-measuring device according to the present invention, wherein, be divided on distance side as a result according to the predetermined possible measurement range of coherent length, to make the displacement of zero position and the shift needle of space reference point realizes each passage thus.For the situation of smooth surface, as net result, all passages will measure identical distance.For this object, by means of delay section, before signal transacting, generate different staggered distances, this distance is known, and takes in when estimating accordingly.Thus, for the reference point of this measurement from passage to channel shift, but can computationally mate.This staggered greatest limit is also determined by the coherent length predetermined at source by maximum measurement range thus at this.
Figure 10 show for distance-measuring device according to the present invention, the schematic illustration figure of the Part II of the course of the beam of the 6th illustrative embodiments with this additional delay section.Optical unit parts 10c is connected to base portion 10a via the connecting pipe 10b of detection termination, and wherein, the optical fiber 15 of this passage also passes through.
In the shell 17 of optical unit parts 10c, optical fiber 15 is coupled in gradient-index lens 19 via the sleeve pipe 18 distributed respectively, and it fills the post of collimating apparatus.In this case, the corresponding transition of sleeve pipe 18 to gradient-index lens 19 is configured for utilizing common path geometry to limit the retro-reflective surface of reference arm.At least for the n-1 in n passage, the single delay section for measuring radiation MS is furnished with in the downstream of the gradient-index lens 19 of each passage, it can realize especially by the glass component 21 that length is different, select according to their length, be assigned the different segment of this coherent length or the different segment of maximum measurement range to make each passage.
The end postponing section 21 is connected to circuit or the matrix of lenticule 22 according to aperture geometry.Due to this delay section, thus, each passage has the single length δ L between the focus as target surface and the transition spool piece 19 for gradient-index lens 19 now i(by determining as the corresponding glass parts 21 postponing section).
These length δ L ithe delay brought thus allows to be separated these passages by Fourier domain during signal transacting.In this illustrative embodiments, also use integrated transmission and receive optical unit, to make from wanting the measuring radiation MS of measured surface back reflection again by lenticule 22 and glass component 21, and by other assemblies.After them, the signal detected again is combined by beam splitter and is coupled in single single-mode fiber, then guides to radiation detector by means of the latter, specifically, radiation detector can also be arranged on outside detection termination, its because of but electric passive.In this case, the amplifier that the loss caused because of beam splitter can be connected by downstream again compensates.
Except the delay section in optical unit parts 10c, relevant delay cell can be used, to avoid the crosstalk between passage.For the Part I of the course of the beam of the 6th illustrative embodiments for distance-measuring device according to the present invention, illustrate in Figure 11 and relevant delay cell has been integrated in base portion 10a, wherein, static color is separated and frequency division multiplexing two kinds of method combinations with one another.
In the shell 11 of base portion 10a, the array waveguide grating as look beam splitter 13 is arranged on the downstream of the single-mode fiber with sleeve pipe 12, as also as shown in Fig. 5 or the first illustrative embodiments.In the downstream of the efferent of beam splitter 13, the measuring radiation being divided into multiple passage is coupled in the individual independent optical fiber 15 of n via many ferrules 14 successively, and wherein each is assigned with frequency or wavelength range delta lambda 1-Δ λ none of in.Optical fiber 15 is directed to colourless 1 × m beam splitter 23 in each case for their part.In the downstream of each beam splitter 23, be furnished with relevant delay cell 24 successively, it is from 1, the output of the indexation of 1 to n, m is combined, to form fibre bundle, and by the mode identical with other illustrative embodiments, guide to optical unit parts via connecting pipe 10b.Having the be concerned with continuity of look beam splitter 13 of delay cell 23 and 24 of downstream is not as shown in this embodiment enforceable at this, and can specifically reverse by its order.These passages have the relevant delay section for avoiding the crosstalk between passage in relevant delay cell, and it can be implemented as optical fiber particularly.At this, from passage L ito passage L i+1relative length separation delta L ibe greater than the coherent length L of lasing light emitter in each case coh.
&Delta;L i = L i + 1 - L i > L coh 2
These are relevant postpones sections at this only for avoiding crosstalk, and thus, they can be omitted in certain special cases, such as, when the enough large spacing of given passage.
The aperture of different passage specifically can be arranged as matrix-like fashion by continuity shown in Figure 12.
Figure 13 exemplified with the ultimate principle for the frequency division multiplexing adopted in the 6th illustrative embodiments of distance-measuring device according to the present invention, at the E field distribution of frequency domain and Fourier transform FT (E) thereof.At moment t, this frequency spectrum is made up of the distribution of different electromagnetic field, and wherein, each passage i has the signal e (f of local oscillator li, t) and target or the signal e (f of target surface ti, t).At this, this passage separates as follows in each case by frequency domain,
&Delta;f ch _ i = 2 &Delta;L i &CenterDot; &gamma; c
Wherein, c indicates the light velocity, and γ indicates the tuning speed of modulated laser source, such as, and 20THz/ms.
Except access needle is to comparatively Large space Δ f each other ch_iin addition, each passage also utilize this spacing to divide local oscillator LO (that is, reference arm) with two component of signals of target (that is, gage beam).
δL i＝L target_i-L LO_i
Wherein, L lO_iand L target_ithe corresponding length of instruction reference arm and gage beam, and the poor δ L thus between them icorrespond to and seek distance for surface.Determine that it is known for seeking distance for these wanting measured surface, in principle, according to such as WO 2009/036861 or there is application number 11171582.7 european patent application in describe prior art.
Figure 15 show for distance-measuring device according to the present invention the 6th illustrative embodiments, under frequency domain the schematic illustration figure of the distribution (being made up of multiple interferogram) of institute's detected intensity or the correspondence of Fourier transform FT (I).

Claims (15)

1., for specifically carrying out an interference distance measurement mechanism for measured surface (4) according to optical coherence tomography principle, this interference distance measurement mechanism at least comprises
-tunable laser, this tunable laser has the coherent length for generating the measuring radiation (MS) utilizing wavelength slope to modulate, and wherein, the described coherent length of described laser instrument limits measurement range,
-beam path, this beam path has
Zero sends optical unit, and this transmission optical unit is used for described measuring radiation (MS) to be transmitted into described surface (4),
Zero receive optical unit, this reception optical unit for receiving the described measuring radiation (MS) from described backscatter,surface,
Zero interferometer, this interferometer is made up of gage beam and reference arm, specifically, has the public course of the beam in local of gage beam and reference arm,
-radiation detector and estimation unit, described radiation detector and described estimation unit for determining the distance from the reference point of described distance-measuring device to described surface (4),
It is characterized in that,
By means of at least one beam splitter (13,20,20 "); be defined for n >=2 passage of parallel launch measuring radiation (MS), described n >=2 passage is assigned with the different subrange of the described wavelength slope for the x time of specifying in each case.
2. distance-measuring device according to claim 1,
It is characterized in that,
Described wavelength slope is divided into n wavelength band of same widths, specifically, is separated discretely, and wherein, passage described in each is assigned with a described wavelength band.
3. distance-measuring device according to claim 1 and 2,
It is characterized in that,
The described subrange of described wavelength slope is separated by look and generates.
4. distance-measuring device according to claim 3,
It is characterized in that,
Described beam splitter (13) is array waveguide grating.
5. distance-measuring device according to claim 3,
It is characterized in that,
Described look is separated and is realized by the look beam splitter of the subrange for wavelength slope described in coupling output, in the assembly of upstream that this look beam splitter is arranged on described transmission optical unit, that be directly arranged in transmitting.
6. the distance-measuring device according to any one in aforementioned claim,
It is characterized in that,
Send optical unit and be embodied as the transmission of combination and reception optical unit (10b) with reception optical unit, the transmission of described combination is specifically coupled to described radiation detector via single single-mode fiber with reception optical unit (10b).
7. the distance-measuring device according to any one in aforementioned claim,
It is characterized in that,
Described passage is arranged in described transmission optical unit by wire or matrix-like fashion.
8. the distance-measuring device according to any one in aforementioned claim,
It is characterized in that,
Described passage is assigned the different subrange of the described measurement range limited by described coherent length in each case.
9. distance-measuring device according to claim 8,
It is characterized in that,
Described passage is assigned in each case by means of the delay section of different length, the different subrange of described measurement range that limited by described coherent length.
10. distance-measuring device according to claim 9,
It is characterized in that,
Passage described at least one has single length δ L between focus and transition spool piece i, described length is by determining as the corresponding glass component postponing section.
11. 1 kinds for specifically carrying out the interfeerometry ranging method of measured surface (4) according to optical coherence tomography principle, the method at least comprises
-measuring radiation (MS) utilizing wavelength slope to modulate is generated by means of the laser instrument with coherent length, wherein, the described coherent length of described laser instrument limits measurement range,
-described measuring radiation (MS) is transmitted on described surface (4),
-receive described measuring radiation (MS) from described backscatter,surface and determine the distance from the reference point of described distance-measuring device to described surface (4) with interference mode,
It is characterized in that,
Described measuring radiation (MS) is via a n >=2 passage parallel launch, and wherein, described passage is assigned with the different subrange of the described wavelength slope for the x time of specifying in each case.
12. range finding arrangement methods according to claim 11,
It is characterized in that,
Described wavelength slope is divided into n wavelength band of same widths, specifically, is separated discretely, and wherein, passage described in each is assigned with a described wavelength band.
13. range finding arrangement methods according to claim 11 or 12,
It is characterized in that,
The described subrange of described wavelength slope is separated by look and generates.
14. distance-finding methods according to any one in aforementioned claim 11 to 13,
It is characterized in that,
Described passage is assigned the different subrange of the described measurement range limited by described coherent length in each case.
15. range finding arrangement methods according to claim 14,
It is characterized in that,
Described passage is assigned in each case by means of the delay of different duration, the different subrange of described measurement range that limited by described coherent length.
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